How can I make Excel conditionally highlight cells based on the contents of cells?

I have a few things that I would like to do on Excel:

1. How do you highlight a row [A-U] if only the first cell A has had text entered in it?
   When you enter text in cell A cells B-U have a yellow background?


2. How do you make the highlighting disappear as you fill the cells?
   When you enter text in any of the B-V cells, they return to the white background?


3. How do you make certain cells not have a yellow background with a key word?
   When you enter "Cats" in cell G, cell H returns to the white background as well as cell G.


4. How do you apply this to the entire Excel sheet?